Life Cycle Analysis
With examples from biofuel analysis
Sustainable Energy
18th November 2010
Outline of Presentation
• Introduction to Life Cycle Analysis (LCA)
• LCA Basics
• Examples and challenges to
implementation
–Corn Ethanol
–Cellulosic Ethanol
–Cellulosic Biofuels
• Illuminating Biofuel Trade­offs
• Consideration of Biofuel Policy
Introduction to LCA
• What is LCA?
– A system analysis methodology (remember toolbox 4?)
– “cradle­to­grave analysis”
Emissions
Energy
Production of
Raw Materials
Wastes
Manufacturing
Process
Wastes
Use of
Product
Wastes
Disposal
Recycle
Wastes
Components of LCA
• Inventory
– Quantification of energy and raw material
requirements, emissions, effluents, and wastes
– i.e. mass and energy balances are integrated over
each process in system
• Impact Assessment
– Values can be assigned to effects for
quantification
• Improvement
– Systems can then be optimized with respect to
parameters from impact assessment
Why is LCA methodology Useful?
• Many parameters we are interested in don’t
occur in just one step of a product’s lifecycle
– Carbon dioxide emissions from Coal­to­Liquid
fuels.
• Optimizing one production step doesn’t mean
system is optimal.
–Hydrogen as a transportation fuel
• Lifecycle analysis is intended to be used to
optimize the aggregate outcomes
Allow for comparison of potential
products: MacDonald’s ­ Styrofoam or
paper?
Oil (bad?)
Trees (natural?)
Chemicals (worse)
Paper (good ?)
Styrofoam (??)
Oil
Chlorine or
Peroxide
Pulp
Paper
PCBs +
Dioxins
Benzene + C2H4 + etc.
Acid or Alkali
Water
Wastewater
Hard to recycle
Plastic coating
Landfill
Trash
CFCs
CO2
Pentane
Styrene
Polystyrene foam
McD
Recycle
Life­Cycle Analysis ­ approach
• Define “cradle­to­grave” alternative systems
• Set system boundary conditions
• Set time basis (snapshot of industry in time vs.
one life cycle of representative product)
• Identify impacts of interest to decision­makers
– Costs, air pollution, GHG emissions, wastes,
resource depletion, etc.
• For each portion of the life­cycle, estimate the
impacts of interest
• Assess overall tradeoffs, considering
uncertainties
• Identify major sources of adverse impact and
assess improvements
Life Cycle Analysis Software
• Dedicated Packages
– GaBi
– Umberto
• DIY (for simple cases)
– Excel
– Matlab
Life Cycle Analysis for Energy
Systems
• Major process
steps
– Resource
extraction/
production
–transport
– Fuel/electricity
production
–Distribution
–end­use
• Important
Parameters
–Emissions
–Useful work
–Costs
• Useful simplification
– Most energy
conversion facilities
non­fuel resource
use negligible.
LCA studies for biofuels are
mandated
• Text of the Energy Independence and Security Act of 2007:
– “GENERAL.—The term ‘advanced biofuel’ means renewable
fuel, other than ethanol derived from corn starch, that has
lifecycle greenhouse gas emissions, as determined by the
Administrator, after notice and opportunity for comment, that
are at least 50 percent less than baseline lifecycle greenhouse
gas emissions.”
– “CELLULOSIC BIOFUEL.—The term ‘cellulosic biofuel’
means renewable fuel derived from any cellulose,
hemicellulose, or lignin that is derived from renewable biomass
and that has lifecycle greenhouse gas emissions, as determined
by the Administrator, that are at least 60 percent less than
the baseline lifecycle greenhouse gas emissions.”
– Baseline: average LCA GHG emissions from gasoline or diesel,
whichever a particular biofuel replaces
• The act calls for 36 billion gallons of renewable fuel by 2022, with
at least 21 billion gallons of this being “advanced biofuels”.
Life­Cycle Analysis – biofuels approach
• Define “cradle­to­grave” alternative systems
– Choose alternate fuel options
• Set system boundary conditions
– This is where the big fights have been/are going to be
• Identify impacts of interest to decision­makers
– Costs, air pollution, GHG emissions, land­use
change, Food Versus Fuel?
• Assess overall tradeoffs, considering
uncertainties
• Identify major sources of adverse impact and
assess improvements
System Boundaries for Biofuels
• Where do we draw the boundaries for our
analysis? Why?
• This turns out to be a MAJOR point of
contention.
– The California Low Carbon Fuel Standard
• If there is a comprehensive carbon tax –
won’t double counting then occur?
The California Low Carbon Fuel
Standard (LCFS)
• The Governor's Executive Order directs
the Secretary for Environmental
Protection to coordinate the actions of the
California Energy Commission, the
California Air Resources Board (ARB), the
University of California and other agencies
to develop the protocols for measuring the
"life­cycle carbon intensity" of
transportation fuels…
California LCFS (Continued)
• In the California rule­making a large fight
revolved around the quantification
secondary land­use changes.
–Argument for inclusion:
• Will include deforestation caused by land use
change to meet demand for food
–Argument for exclusion:
• Double counting
• Measuring a counterfactual
• Not applied to petroleum baseline
System Boundaries for Biofuels
(Revisited)
• Policy is likely to play a major role in defining
system boundaries
– The term ‘advanced biofuel’ means renewable
fuel, other than ethanol derived from corn starch,
that has lifecycle greenhouse gas emissions, as
determined by the Administrator, after
notice and opportunity for comment, that are at
least 50 percent less than baseline lifecycle
greenhouse gas emissions.”
• Assuming that system boundaries are “non­
overlapping” could there still be double
counting?
Identifying the Process Steps
• System contains a
connected web of
individual processing
steps each with their
own:
– Energy balances
– Mass balances
– Cash flows
– Emissions
– Regulations
– …
• How do we determine
the necessary amount
of granularity?
– Only major steps?
– Every subprocess?
– Down to the last valve?
• This is a matter of
identifying goals of
analysis (think back
to SD lecture)
Key Issues
System Boundary
Biomass
Harvest
Transportation
Conversion
Fuel
Image by MIT OpenCourseWare.
17
• Scale ­­ Biomass availability
• Performance ­­ Energy balance
• Economics today and tomorrow
• transitioning from corn–based to
cellulosic fuel
MIT
Simplified Lifecycle of Biofuel
Production
Energy Inputs to Corn Ethanol
Total Ethanol
Distill/Dry
Electricity
Distribution
Other
Corn
0
10
20
30
MJ/kg EtOH
Courtesy of Jeremy Johnson. Used with permission.
40
Energy Inputs to Corn
Machinery
Seeds
Electricity
Pesticide
Lime
P­K
Nitrogen
Irrigation
Fossil Fuels
0
MJ/kg EtOH
5
Courtesy of Jeremy Johnson. Used with permission.
Corn Ethanol – comparison of
estimated net energy ratio.
Argonne (1999)
USDA (2004)
ORNL (1990)
UCBerkeley A (2006)
UCBerkeley B (2006)
Effect of common
system boundaries,
coproduct credit
Amoco (1989)
Iowa State (1992)
Pimentel (2005)
MIT (2006)
0.5
0.75
1
1.25
1.5
Net Energy Ratio
Courtesy of Jeremy Johnson. Used with permission.
1.75
Corn Ethanol
Key conclusions
• Corn grain ethanol has a slightly positive net energy on
average, but is very dependent on
– Ethanol production efficiency
– Location and practices in corn production
– Transportation distances
• Improved corn yield, conversion and purification
technology can help, but most gains are incremental
• Expansion of corn production will probably lead to
more energy intensity
22
MIT
Cellulosic Ethanol – Fossil fuel
energy requirements
Tiffany Groode, PhD MIT 2008
Courtesy Tiffany Groode. Used with permission.
GHG Emissions – Cellulosic
Ethanol
Tiffany Groode, PhD MIT 2008
Courtesy Tiffany Groode. Used with permission.
Net Energy Value ­ Cellulosic
Ethanol
Tiffany Groode, PhD MIT 2008
Courtesy Tiffany Groode. Used with permission.
GHG Cellulosic Ethanol
Tiffany Groode, PhD MIT 2008
Courtesy Tiffany Groode. Used with permission.
Conclusions ­ Ethanol
• Corn grain ethanol:
– Considering economics, energy balance, GHG abatement,
not a bad idea, but limited by land constraints
– Considerable expansion of corn production negates any
benefits, so subsidies should be restructured to efficiency
• Lignocellulosic ethanol
– Significantly better environmental performance plus
more availability, but economic cost is a large barrier
– Multiple technology advancements must be made to
achieve commercialization, with feedstock logistics
critical
• Overall
– Potential for non­negligible (~20%) replacement of
petroleum, but significant investment is required
27
MIT
Why Ethanol?
• If one is to use synthetic chemistry, one
can make fuels that are not metabolic
products:
– Synthetic Hydrocarbons (Synthetic Natural
Gas, Fischer­Tröpsch Diesel, MTG Gasoline)
– Other Alcohols (methanol, propanol,
butanol+)
–Dimethyl Ether
–Hydrogen?
Properties of possible fuels
Density
(g/cm3)
Lower Heating
Value (MJ/kg)
20
26.9
30.5
33
44
Heat of
Vaporization
(KJ/kg)
1103
840
790
580
350
Fuel
Formula
Molecular
Weight
Methanol
Ethanol
Propanol
Butanol
MTG Gasoline
CH3OH
CH3CH2OH
CH3(CH2)2OH
CH3(CH2)3OH
CH1.85
32.04
46.07
60.1
74.14
~110
0.792
0.785
0.8
0.81
0.75
Fuel
Formula
Molecular
Weight
Density
(g/cm3)
Lower Heating
Value (MJ/kg)
DME
Fischer-
Tröpsch Diesel
CH3OCH3
46.07
0.668
28.7
Heat of
Vaporization
(KJ/kg)
467
CH1.8
170
0.8
43
270
Life Cycle Energy Efficiency of
Thermochemical Biofuels
Biomass-to-Wheel Efficiency utilizing best possible distribution method for each fuel
Methanol
Ethanol
Mixed Alcohols
MTG
DME
FT Diesel
0.0%
A. Stark MIT 2008
5.0%
10.0%
15.0%
20.0%
Efficiency %
25.0%
30.0%
35.0%
Biomass­to­Tank Efficiency of
Thermochemical Biofuels
Biomass-to-Tank Efficiency utilizing best distribution method for each fuel
Methanol
Ethanol
Mixed Alcohol
MTG
DME
FT Diesel
0.0%
10.0%
20.0%
30.0%
40.0%
Efficiency %
50.0%
60.0%
70.0%
80.0%
Fuel Integrability
Fuel
Methanol
Ethanol
Mixed
Alcohol
MTG
Synthetic
Gasoline
FT Diesel
DME
methanol
ethanol
MTG
FTD
DME
Truck
Y
Y
Rail
Y
Y
Pipeline
N
N
Y
Y
N
Y
Y
Y
Y
Y
Y
Y
Y
Y/N
cost of
shipping per
liter 1000km
$0.050
$0.050
$0.003
$0.003
$0.060
cost of
shipping per
GJ 1000km
$3.141
$2.185
$0.101
$0.095
$3.130
• A fuel’s properties will
dictate whether it is
accepted into the
current fuel
infrastructure
• This will greatly
impact the economics
of distribution
End­Use emissions Regulations
• Existing emissions regulations will also play a
role in dictating which fuels are used.
– The Clean Air Act
– Oxygenate requirements
– Zero Emission Vehicles
– California
methanol
ethanol
mixed alcohol
MTG synthetic gasoline
FT Diesel
DME
CO
Slight reduction
Slight reduction
Slight reduction
No change
Moderate reduction
No change
NOx
Significant reduction
Significant reduction
Slight reduction
Slight increase
Moderate reduction
Moderate reduction
Particulates
N/A
N/A
N/A
N/A
Moderate reduction
Significant Reduction
•Food Versus Fuel
•Land­use changes
ILLUMINATING THE
TRADE­OFFS
Food Versus Fuel
• Increasing demand for biofuels may
incentivize farmers to switch land away from
food production
–Decreasing food supplies
–Increasing food prices
• Some argue that this was the case in 2008.
– Data for making a conclusion either way is
somewhat lacking.
– Innovation in agriculture is far outpacing demand
growth.
Land­use Changes
• Increasing demand
for biofuels may
incentivize farmers to
put more land into
production
– The rainforests for
Photo of soya growing in Brazil removed due to copyright restrictions.
soy/sugar cane
– Jatroptha in Indonesia
• How do we quantify
these secondary
effects?
– Measuring a
counterfactual
The Biofuel Policy Landscape
• Blender­Tax Credits (Volumetric Ethanol
Excise Tax Credit, VEETC)
– 45 cents per gallon tax credit for ethanol
blenders.
– This year ~9 billion gallons of ethanol were
used
– This subsidy creates a perverse incentive to
produce low energy density fuels (ethanol
instead of Fischer­Tröpsch Diesel)
Biofuel Policy Landscape (cont.)
• The Energy Independence and Security
Act (EISA) requirements
– In 2022 36 billion gallons of biofuel use is
mandated
• Of this, majority must be advanced/cellulosic
–We are not meeting this target.
• EPA limits the percentage of ethanol
which can be blended in RFG
–Oxygenate requirements
–Blending wall
General Conclusions
• No one fuel constitutes a silver­bullet
• Technology specific subsidies have not
worked and are likely not to work
• US biofuel policy is very friendly to
ethanol and will make it hard for other
fuels to enter the market
• System thinking is necessary in analyzing
such complex value chains
MIT OpenCourseWare
http://ocw.mit.edu
22.081J / 2.650J / 10.291J / 1.818J / 2.65J / 10.391J / 11.371J / 22.811J / ESD.166J
Introduction to Sustainable Energy
Fall 2010
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